The use of heteropolysaccharides as viscosifying agents in many food and industrial applications is well known. Typically, these agents are used because of their ability to thicken aqueous solutions at relatively low concentrations. Xanthan gum (a biopolymer produced by aerobic fermentation in a nutrient medium of the organism X. campestris), S-194 (a biopolymer produced by aerobic fermentations in a nutrient medium of the Alcaligenes organism ATCC 31961, described in U.S. Pat. No. 4,401,760), and guar gum (an extract of the seed of the guar plant, Cyanaposis tetragonolobus, family Leguminosae) are three such known polysaccharides. These gums are known in various forms. For example, guar gum derivatives include oxidized guar, carboxymethylated guar, hydroxyalkylated guar, etc. Xanthan gums of different pyruvate levels (EP 66,961) and calcium levels (e.g., U.S. Pat. No. 4,375,512, Richmon) are known. Xanthan gums of altered rheology have also been described. For example, U.S. Pat. No. 4,299,825 teaches a "low viscosity" xanthan gum having an 8-15 wt. % viscosity of 10,000-20,000 cP.
Bipyridinium (also known as bipyridylium) quaternary salts such as those of U.S. Pat. No. 4,118,218 are useful herbicidal compounds. Of these, paraquat (1,1'-dimethyl-4,4'-bipyridinium dichloride) and diquat (6,7-dihydrodipyrido (1.2-a; 2'.1'-c) pyrazinediium dibromide) are the most commonly used. These compounds are typically sold commercially as aqueous compositions. Attempts at preparing free flowing wettable powder formulations of these salts have not proved successful. UK 2,100,603 describes wettable powder compositions using powdered calcium silicate as a carrier. J5 6152-401 (Asahi Chemical) describes powdered compositions comprising inorganic sulphate salts of sodium, magnesium, etc. and anti-caking compounds such as white carbon, borax, silica gel, etc. U.S. Pat. No. 4,118,218, which is incorporated herein by reference, describes a process for preparing granular herbicidal compositions which comprises depositing an aqueous solution of the bipyridinium quaternary salts on inert carriers, preferably calcium or sodium chloride. This patent also refers to various Japanese and U.K. patent applications which teach solid herbicidal compositions. None of these compositions has been commercially successful. Generally, the prior art compounds have not been sufficiently concentrated in active ingredients, have not hydrated properly, or have not prevented crystallization of the active ingredient, thus posing a potential hazard to handlers of the dry powders. Crystallization occurs on drying of aqueous solutions of the herbicidal bipyridinium salts. Crystals also appear in the dry compositions of these salts.